Jenkins Pipeline: Supporting APIs Plugin 838.va_3a_087b_4055b and earlier does not sanitize or properly encode URLs of hyperlinks sending POST requests in build logs, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers able to create Pipelines.
Jenkins Pipeline: Supporting APIs Plugin 2.17 and earlier have an arbitrary code execution due to incomplete sandbox protection: Methods related to Java deserialization like readResolve implemented in Pipeline scripts were not subject to sandbox protection, and could therefore execute arbitrary code. This could be exploited e.g. by regular Jenkins users with the permission to configure Pipelines in Jenkins, or by trusted committers to repositories containing Jenkinsfiles.